Electronic devices such as a smartphone and a tablet computer use a liquid crystal display (English: Liquid Crystal Display, LCD for short) as a display component.
The LCD can perform normal display only by using a backlight provided by a backlight circuit. The backlight circuit is controlled by a backlight controller. The backlight circuit includes a backlight power supply chip and a backlight light emitting diode (English: Light Emitting Diode, LED for short) connected to the backlight power supply chip. In an operating process, the backlight power supply chip receives a pulse-width modulation (English: Pulse-Width Modulation, PWM for short) signal sent by the backlight controller. The backlight power supply chip outputs a drive current to the backlight LED according to the pulse-width modulation signal. The backlight LED emits a backlight according to the drive current. A magnitude of a drive current and a backlight intensity are in a positively correlated relationship, that is, a larger drive current indicates a higher backlight intensity, and a smaller drive current indicates a lower backlight intensity.
Limited by hardware performance of a backlight power supply chip, a magnitude of a drive current that is output by the backlight power supply chip falls within a limited range. As a result, backlight luminance that is output by a backlight LED also falls within a limited luminance range. In other words, the lowest luminance or the highest luminance that is output by the backlight LED is not expected ideal luminance of developers in design or limiting luminance that can be actually output by the backlight LED.